4-Ketocyclophosphamide is a metabolite of cyclophosphamide. Cyclophosphamide (trade names Endoxan, Cytoxan, Neosar, Procytox, Revimmune), also known as cytophosphane, is a nitrogen mustard alkylating agent, from the oxazophorines group. An alkylating agent adds an alkyl group (CnH2n+1) to DNA. It attaches the alkyl group to the guanine base of DNA, at the number 7 nitrogen atom of the imidazole ring. It is used to treat various types of cancer and some autoimmune disorders. (Wikipedia)